Ping[2]: [PATCH v2] Allow shrinking of arena heaps using mmap based on overcommit settings when available

[Siddhesh Poyarekar]

ping!

regards,
Siddhesh

On Mon, 17 Sep 2012 11:16:55 +0530, Siddhesh wrote:
> Hi,
> 
> Ping?
> 
> Regards,
> Siddhesh
> 
> On Tue, 11 Sep 2012 15:40:36 +0530, Siddhesh wrote:
> 
> > Hi Roland,
> > 
> > Here is an updated patch with further fixes as per your review. No
> > regressions in the testsuite. Also, I have tested this on F16 x86_64
> > as follows:
> > 
> > * echo 0 > /proc/sys/vm/overcommit_memory
> > * Run the benchmark program that I posted earlier:
> > 
> > http://sourceware.org/ml/libc-alpha/2012-08/msg00462.html
> > 
> > and attach an strace as follows:
> > 
> > strace -f -e madvise -p $(pgrep a.out)
> > 
> > to confirm that madvise is being called. Detach and attach strace
> > again as follows:
> > 
> > strace -f -e mmap -p $(pgrep a.out)
> > 
> > to ensure that there are no mmap calls with MAP_FIXED.
> > 
> > Now disable overcommit:
> > 
> > * echo 2 > /proc/sys/vm/overcommit_memory
> > * Run the benchmark program and verify that the behaviour is the
> >   opposite, i.e. there should be no calls to madvise and you should
> > see calls to mmap with MAP_FIXED.
> > 
> > Further, I also verified that I see the performance difference
> > between madvise and MAP_FIXED:
> > 
> > with overcommit_memory == 0:
> > 
> > RUNS=4096, TOTAL=8859615.000000, AVG=2162.991943
> > RUNS=4096, TOTAL=8948967.000000, AVG=2184.806396
> > RUNS=4096, TOTAL=9002337.000000, AVG=2197.836182
> > RUNS=4096, TOTAL=9147284.000000, AVG=2233.223633
> > RUNS=4096, TOTAL=8852469.000000, AVG=2161.247314
> > RUNS=4096, TOTAL=8920974.000000, AVG=2177.972168
> > RUNS=4096, TOTAL=9051495.000000, AVG=2209.837646
> > RUNS=4096, TOTAL=8896417.000000, AVG=2171.976807
> > 
> > with overcommit_memory == 2:
> > 
> > RUNS=4096, TOTAL=9916217.000000, AVG=2420.951416
> > RUNS=4096, TOTAL=10098292.000000, AVG=2465.403320
> > RUNS=4096, TOTAL=9951147.000000, AVG=2429.479248
> > RUNS=4096, TOTAL=9776165.000000, AVG=2386.759033
> > RUNS=4096, TOTAL=9735272.000000, AVG=2376.775391
> > RUNS=4096, TOTAL=10049977.000000, AVG=2453.607666
> > RUNS=4096, TOTAL=9967350.000000, AVG=2433.435059
> > RUNS=4096, TOTAL=9817866.000000, AVG=2396.939941
> > 
> > Regards,
> > Siddhesh
> > 
> > ChangeLog:
> > 
> > 	* malloc/arena.c: Include malloc-sysdep.h.
> > 	(shrink_heap): Use check_may_shrink_heap to decide if
> > madvise is sufficient to shrink the heap or an unmap is needed.
> > 	* sysdeps/generic/malloc-sysdep.h: New file.  Define
> > 	new function check_may_shrink_heap.
> > 	* sysdeps/unix/sysv/linux/malloc-sysdep.h: New file.  Define
> > 	new function check_may_shrink_heap.
>